Metastable Bi8Ni8S by Reductive Pseudomorphosis of Bi8Ni8SI2

Abstract

AbstractThe bimetallic subsulfide Bi8Ni8S was synthesized by reduction of Bi8Ni8SI2withn‐BuLi. Bi8Ni8S is metastable and decomposes exothermically at about 180 °C. In a pseudomorphosis, the shiny black crystals of the precursor were preserved, while the iodide ions were extracted and the pre‐formed$\rm^1_\infty$[Bi8Ni8S] fragments rearranged into a pseudo‐hexagonal rod packing [space groupPbam,a= 1750.14(7) pm,b= 1007.7(2) pm,c= 419.6(3) pm]. The rods have an effective diameter of about 1 nm and consist of an outer octagonal tube of bismuth atoms and an inner octagonal tube of nickel atoms. This arrangement markedly resembles the columnar Ta4Te4Si structure type. The difference comes with the disulfide groups that reside on the central axis. Interatomic distances inside the rods are almost not affected by the reduction, and thus the electronic band structure is not much altered. Yet, the additional electrons raise the Fermi level into a local maximum of the density of states and occupy predominantly antibonding Ni–Ni and S–S states. The dominant Bi–Ni multicenter bonding is accompanied by localized two‐center bonds between nickel atoms. The charges of the nickel atoms as well as ELI‐D basin populations of Ni–Ni and Ni–Bi bonds change considerably, indicating that the tube is (un)charging quite flexibly and acts as an electron reservoir. In contrast to the iodide precursor, the weak Pauli paramagnetism of Bi8Ni8S is slightly enhanced and spin correlations are observed below 20 K.